COUTANT: WOOD PERIDERM IN CERTAIN CACTI 359 
FIG, 2. ag ti tion through a five-day-old wound of an Opuntia 
versicolor plant, X 24; the open white areas consist of normal cellulose-walled cells; 
starch is found only in regions indicated. a, epidermal cells, with heavily cutinized 
outer walls; 6, hypodermal tissue; c, cellulose-walled cells, containing stored starch; 
d, vascular bundles; e, cells, the walls of whi ve me discolored and lignified; 
f, cells, the walls of which have become discolored; g, suberized, thin-walled cells, 
produced through action of the first wound-meristem. 
